Process of thermally cracking a petroleum oil



3,019,272 PROCESS OF THERMALLY CRACKING A PETROLEUM OIL Filed Aug. 2, 1957 Jan. 30, 1962 A. STEINHOFER EIAL 2 Sheets-Sheet 1 SECOND STAGE THERMAL CRACKER FIG. 1.

iZf

DISTILLATION COLUMN FIRST STAGE THERMAL CRACKER INVENTORS ADOLF STE/NHOFER EBA/ST BART/1'01. 0M5 07'7'0 FEE) x ii,

ATTORNEY HEL MUT A/ONAIENMAC/IER 3,019,272 PROCESS OF THERMALLY CRACKING A PETROLEUM OIL Filed Aug. 2, 1957 Jan. 30, 196 A. STEINHOFER EI'AL 2 Sheets-Sheet 2 sEcoNo STAGE THERMAL CRACKER DISTILLATION COLUMN FIRST STAGE THERMAL CRACKER FIG.2.

INVENTORS AooLF STEl/VHOFEA ERNST BART/10L OME orro FEEY l/EL M IVO/VENMACWEI? BY M ATTORNEY United States Patent 3,019,272 PROCESS 0F THERMALLY CRACKING A PETRQLEUM GIL Adolf Steinhofer, Ludwigshalen (Rhine), Ernst Bartholome, Heidelberg, and Otto Frey and Helmut Nonnemacher, Ludwigshafen (Rhine), Germany, assignors to Badische Anilin- & Soda-Fabrik Airtiengesellschaft, Ludwigshafen (Rhine), Germany Filed Aug. 2, 1957, Ser. No. 675,952 priority, application Germany Aug. 2, 1956 13 Claims. (Cl. 260-683) This invention relates to a new and improved process for cracking oils for the production of gaseous olefins, preferably ethylene and propylene. It is already known to crack gaseous or liquid hydrocarbons at high temperatures on solid heat resisting non-oxidisable or carbonaceous substances for the production of gaseous olefins, especially ethylene. The solid substances are present in the reaction chamber in a fixed or moving bed or in fluidised state (fluidised layer). The heat necessary for the reaction can be supplied to the reaction chamber in various ways. In the so-called autothermal method the reaction heat is directly generated in the reaction chamber, for example by combustion of a part of the hydrocarbon with oxygen-containing gases. In the method with circulating heat carriers, a part of the solid is continually withdrawn from the reaction chamber, transferred to a heating chamber, heated up and returned to the reaction chamber.

in the production olefins by thermally cracking mineral oils, mineral oil residues or substances of similar constitution, which contain vaporisable and non-vaporisable components in a wide boiling range, all these methods have been attended by a serious disadvantage in that, in spite of careful correlation of the residence time and the reaction temperature, it has not been possible to avoid the formation of large amounts of undesirable byproducts at the expense of the yield of gaseous olefins. Many of these byproducts, such as carbon black, resinous and asphaltic polymerisation products, render diflicult the carrying out of the cracking continuously and render necessary considerable expenditure from the point of view of process technique and apparatus. Another part of the byproducts, especially the liquid cracked products of high boiling point, require a troublesome and expensive aftertreatment or working up in order to convert them into standard commercial products. Since these cracked products consist to a large extent of components which are still capable of being cracked on the one hand and polymers of unsaturated, especially gaseous, compounds on the other hand, the production of these less valuable products results in a correspondingly smaller yield of valuable gaseous olefins.

We have now found that the said disadvantages are avoided by separating the initial material into a distillation residue and a distillate, cracking the distillation residue in a first stage at temperatures of 630 to 800 C. in a fluidised layer of granular solids of which the outer shell is formed by coke formed by the cracking, and cracking the distillate in a second stage at a temperature between 720 and 900 C., but at least 20 C. higher than in the first stage, on heat resisting non-oxidisable and/or carbonaceous substances. As granular solids for the fluidised layer of the first stage and also for the second stage may be used heat resisting natural or synthetic inert substances containing oxides of magnesium, silicon and/or aluminum or carbonaceous substances as coke i.e. high temperature coke and preferably coke produced in the first stage of the cracking.

Thefirst stage of the cracking, which is carried out in a fluidised layer, is characterised by the fact that the Claims cracking is carried out at temperatures of 630 to 800 C., preferably 680 to 760 C., i.e. 700 to 740 C., under coke-forming conditions. The residence time of the reaction products in the reaction chamber, with reference to the empty space, amounts to 0.5 to 10 seconds, in the preferred temperature range 0.75 to 5 seconds. If at the beginning of the cracking heat resisting non-oxidisable or carbonaceous substances from an extraneous source are used in the fluidised layer, these become cov ered with the oil coke formed by the cracking in the form of a shell, and the height of the fluidised layer grows so that solid substances must be continually withdrawn from the cracking process. To maintain a definite grain size distribution it is possible to supply periodically or continuously to the reaction chamber a certain amount of solids from an extraneous source and to withdraw a cor responding amount of, oil coke.

In order to introduce the heat necessary for the reaction, the solid substances can continuously be transferred from the reaction chamber into a combustion chamber, heated up therein, preferably by burning a part of the cracked oil residue boiling above about 300 C. formed by the cracking, and returning it to the reaction chamber. The heat can however also advantageously be introduced autothermally by introducing oxygen-containing gases, especially a mixture of oxygen and steam, into the reaction chamber. In order to maintain coke-forming conditions when working in this Way, i.e. to form in all more coke than is burnt, it is sometimes necessary to return a certain amount of cracked oil residue boiling above about 250 C. and containing carbon black to the reaction chamber. A preferred embodiment of this method of working consists in returning the said cracked oil residue in exactly such an amount that it is completely burnt or coked in the reaction chamber so that no cracked oil residue occurs as a byproduct in the process.

In the second cracking stage the distillate is cracked at temperatures between 720 and 900 C., preferably between 750 and 870 C., i.e. between 800 and 840 C., on heat resisting non-oxidisable granular solids or carbonaceous solids. The temperature should lie at least 20 0, preferably at least 40 C., advantageously at least 50 0, higher than in the first stage. The residence time of the reaction products in the reaction chamber as a rule lies between 0.1 and 2 seconds, preferably between 0.2 and 0.7 second, with reference to the empty space. The heat necessary for the maintenance of the reaction temperature in the second stage can be supplied by continuously transferring solids from thi stage into a combustion chamber, heating them up therein to temperatures of about 800 to 1,200 C. by combustion of the carbon precipitated on the solids during the cracking and also further fuels, and returning the heated solids to the cracking zone of the second stage. In this embodiment of the process it is advantageous to use the cracked oil boiling above about C. arising in the first stage as fuel for the second stage. The heat necessary for the second stage can however also be introduced autothermally, into the reaction chamber, i.e. by the supply of oxygen. As the solids for the cracking and simultaneous fuel there are then preferably used the oil coke formed in the first stage.

The cracking is in general carried out in both stages at atmospheric or slightly increased pressure. Higher pres sures, for example of 2 to 30 atmospheres, may however be used in one or both stages.

Mineral oils, shale oils, tars, their fractions or conversion products, for example cracking or hydrogenation products, come into question as initial materials. The separation by distillation takes place in the usual way, if desired under reduced pressure and/or While supplying steam. The distillatefraction amounts to about 20 to 70% by weight, advantageously 30 to 50% by weight, with reference to the initial material.

By working according to the present invention it is possible to produce from the said raw materials a high yield of ethylene besides a Considerable amount of propylene. If the raw materials are reacted without separation in the fluidised layer method or by another method, for example with heat carriers moved in circulation, it is not possible to achieve equally high yields. In particular it is not possible by the known methods to utilise the initial materials to such a high extent for the production of valuable substances and to avoid the formation of undesirable byproducts.

The following examples will further illustrate this invention but the invention is not restricted to these examples. The examples are given with respect to FIG- URES 1 and 2 of the accompanying drawings, but the invention' is not limited to the said drawings.

Example 1 This example is given with reference to FIGURE 1. 1,000 kilograms of a Near East crude oil (a) together with 200 kilograms of steam (b) are heated up per hour in a preheater 1 to about 250 C. and separated in an attached column 2 into 330 kilograms of distillate and 670 kilograms of distillation residue. The hot distillation residue is introduced through pipe 3 into a fluidised layer 4 which consists of oil coke in a granulation up to 3 millimetres. At the beginning of the process, coke granules can be introduced through feed hopper 23. The fluidised layer is'situated in a shaft furnace 5 having a cross-sectional area of 1 square metre on a metal grate 6 provided with fine slots. A mixture of 400 kilograms of superheated steam (c) and about 180 Nm of oxygen (d) is blown in each hour through pipe 7. A small amount of coke formed by the oil is returned to the layer 4 from the funnel and connecting tube 20. The gases and vapours escaping through pipe 8 are supplied to a washing and separating plant (not shown). The hydrocarbons boiling above about 250 C. obtained therefrom are returned in an amount of about 300 kilograms per hour together with the carbon black formed by the cracking and the dust entrained by the cracking gas, to the fluidised layer through pipe 9. The amount of oxygen is regulated so that a reaction temperature of about 720 C. prevails in the fluidised layer. The excess oil coke is withdrawn from the layer 4 through the outlet pipe 21. In this first stage there are produced about 134 kilograms of ethylene, 94 kilograms of propylene and 54 kilograms of unsaturated (L -hydrocarbons as well as 70 kilograms of aromatic hydrocarbons boiling up to about 150 C. per hour. There are also formed 60 kilograms of a distillate fuel oil containing naphthalene, about 30 kilograms of oil coke and a residual gas of high calorific power which contains large amounts of carbon monoxide and hydrogen.

The vaporous distillate is introduced together with the steam admixed prior to the preheater 1 through pipe 10 into the lower part of a reaction chamber 11 filled with corundum balls 6 millimetres in diameter, the cross-sectional area of the chamber 11 being 0.22 square metre, and flows therethrough upwards in countercurrent to the corundum balls flowing downwardly as a compact filling. The halls after leaving the reaction chamber 11 are conveyed through a lift 12 with the aid of conveyer gas introduced at F into a combustion chamber 13 arranged about the reaction chamber 11. In the chamber 13 the balls are heated up by burning the coke deposited on them,

the cracked oil of high boiling point obtained (e) and an.

additional amount of 30 kilograms of distillate heating oil occurring in the first stage (e) (burnt in chamber 14 which is supplied with air at f) and again supplied to the reaction chamber 11 into the downwardly migrating filling. About 3.3 metric tons of corundum balls circulate each hour. The reaction gases and vapours have a temperature of about 830 C. at the outlet 15 from the reaction chamber 11. Sealing steam can be supplied at S and S and a dosing gas at D.

In this second stage there are produced about 112 kilograms of ethylene, 56 kilograms of propylene and 25 kilograms of higher gaseous olefines as well as 31 kilograms of low-boiling aromatic hydrocarbons per hour. Moreover there is obtained a residual gas of high calorific value which contains considerable amounts of carbon monoxide and hydrogen.

In both stages there are therefore produced in all:

246 kilograms of ethylene kilograms of propylene 79 kilograms of unsaturated C -hydrocarbons 101 kilograms of low-boiling aromatic fraction (end boiling point 150 C.) as well as 60 kilograms of oil coke+distillate fuel oil and a residual gas of high calorific power and with considerable amounts of carbon monoxide and hydrogen.

Example 2 This example is given with reference to FIGURE 2. 1,000 kilograms of a Near East crude oil are heated per hour in a preheater 1 to about 300 C. and separated in an adjacent column 2 into 330 kilograms of distillate and 670 kilograms of distillation residue. The hot distillation residue is introduced through pipe 3 into a fluidised layer 4 which at the beginning of the experiment consists of anthracite introduced through hopper 23 in a. granulation of up to 3 millimetres. The fluidised layer is situated in a shaft furnace 5 of a cross-sectional area of 1 square metre on a metal grate 6 provided with fine slots. A

mixture of 400 kilograms of superheated steam (c) and about 180 Nm of oxygen (d) are blown in per hour through pipe 7. As in Example 1, a small amount of coke formed by the oil is returned to the layer 4 from the funnel and connecting tube 20. Also, the gases and vapours escaping through pipe 8 are supplied to a washing and separating plant (not shown). The hydrocarbons boiling above about 250 C. formed by the cracking and separated from the gases taken off through line 8 are returned in an amount of about 300 kilograms per hour together with the carbon black formed by the cracking and a part of the dust entrained by the cracking gas, into the fluidised layer through pipe 9. The amount of oxygen is regulated so that a reaction temperature of about 720 C. prevails in the fluidised layer. Solids are withdrawn continuously from the fluidised layer through outlet pipe 21 so that the height of the fluidised layer is kept constant. After operation for some days the fluidised layer only still contains solids the outer shells of which consist of coke formed by the cracking. The withdrawn solids are separated into the fractions 0 to 0.01, 0.01 to 0.75, 0.75 to 2, and greater than 2 millimetres and the fraction 0.75 to 2 millimetres returned to the fluidised layer.

In the first stage there are produced about 134 kilograms of ethylene, 94 kilograms of propylene and 54 kilograms of unsaturated C -hydrocarbons as well as 110 kilograms of aromatic hydrocarbons boiling at 220 C. Moreover there occur 20 kilograms of distillate fuel oil, 33 kilograms of coke (25 kilograms thereof being of 0 to 0.75 millimetre) and a residual gas of high calorific value with large amounts of carbon monoxide and hydrogen.

The vaporous distillate is mixed with a mixture of about 80 Nm of oxygen (g) and 200 kilograms of superheated stem (12) in a mixer 16 and this mixture is introduced into a second fluidised layer 18 which consists of the oil coke fraction of 0.01 to 0.75 millimetre from the first stage. The fluidised layer is situated in a shaft furnace 17 of the same cross-sectional area as the shaft furnace 5 of the first stage. The amount of oxygen is regulated so that a reaction temperature of about 820 C. prevails in the fluidised layer. About 5 kilograms of oil coke are Withdrawn per hour from the fluidised layer through pipe 19 and about 18 kilograms of oil coke of 0.01 to 0.75 millimetre from the first stage are supplied from outlet 21 to the feed hopper 24 while keeping the fluidised layer 18 constant. In the second stage there are produced about 100 kilograms of ethylene, 51 kilograms of propylene and 23 kilograms of un- Saturated C -hydrocarbons as well as 30 kilograms of low-boiling aromatic hydrocarbons. Furthermore there occur a residual gas rich in carbon monoxide and hydrogen and about kilograms of distillate fuel oil.

In the two stages there are therefore produced in all:

234 kilograms of ethylene,

145 kilograms of propylene,

77 kilograms of unsaturated C -hydrocarbons and 140 kilograms of low-boiling aromatic hydrocarbon fraction (with end boiling point 220 C.), as well as about 45 kilograms of oil coke+distillate fuel oil and a residual gas with large amounts of carbon monoxide and hydrogen.

From the foregoing examples, it will be recognized that the invention is particularly useful in the treatment of a crude petroleum oil as the initial material.

We claim:

1. In a process for thermally cracking a crude petroleum oil on a granular solid substance selected from the group consisting of inert heat-resisting non-oxidizaole solids and carbonaceous solids at temperatures of 630 C. to 900 C. for the production of gaseous olefines, the improvement which comprises separating the initial crude petroleum oil into essentially two components, a distillation residue and a distillate fraction, said distillate fraction amounting to about 20 to 70% by weight with reference to the initial oil and said residue constituting substantially the remaining portion by weight with reference to said initial oil, thermally cracking the distillation residue in a first stage at a temperature of about 680 C. to 760 C. in a fluidized layer of said granular solid substance having at least an outer shell formed from coke produced by said cracking in said first stage, and thermally cracking the distillate fraction in a second stage, also on a granular solid substance, at a temperature of about 750 C. to 870 C. but at least about 40 C. higher than the temperature in said first stage.

2. The process as claimed in claim 1 wherein coke produced in the first stage of cracking is used as solid substance in this stage.

3. The process as claimed in claim 1 wherein the cracking is carried out in the presence of a gas selected from the group consisting of steam and carbon dioxide.

4. The process as claimed in claim 1 wherein the heat necessary for the reaction in the cracking zones is introduced by transferring the said granular solid substances from the reaction chamber into a combustion chamber, heating them up and returning them to the reaction chamber.

5. The process as claimed in claim 1 wherein the heat necessary for the reaction in the cracking zones is supplied by introducing oxygen-containing gas into the reaction chambers.

6. The process as claimed in claim 1, wherein the heat necessary for the reaction in the first cracking zone is supplied by introducing oxygen containing gas into the first cracking zone and the heat necessary for the reaction in the second cracking zone is introduced by transferring the said granular solid substances from the second cracking zone into a combustion chamber, heating them up and returning them to the second cracking zone.

7. The process as claimed in claim 1 wherein in order to form more coke than is burnt, an amount of cracked oil residue boiling above about 250 C. and containing carbon black is returned to the reaction chamber of the first cracking stage.

8. The process as claimed in claim 7 wherein the excess of coke formed from the oil in the first stage is used as fuel for cracking in the second stage.

9. The process as claimed in claim 1 wherein the said distillate used as initial material for the second stage amounts to about 30 to 50% by weight with reference to the total initial crude petroleum oil.

10. The process as claimed in claim 1 wherein the cracking is carried out in the first stage at a tempera ture of 700 to 740 C. and in the second stage at a temperature of 800 to 840 C. and the said distillate used as initial material for the second stage amounts to 30 to 50% by Weight with reference to the total initial oil.

11. The process as claimed in claim 1 wherein the pressure in each of said stages is from atmospheric pressure up to about 30 atmospheres.

12. The process as claimed in claim 11 wherein the residence time of the gaseous reaction products in the first stage is about 0.75 to 5 seconds and the residence time of the gaseous reaction products in the second stage is about 0.2 to 0.7 second.

13. The process as claimed in claim 11 wherein at least part of the excess coke formed by cracking the oil residue in the first stage is employed as a carbonaceous fuel for cracking in the second stage.

References Cited in the file of this patent UNITED STATES PATENTS 2,271,645 Kanhofer Feb. 3, 1942 2,338,020 Barron Dec. 28, 1943 2,340,974 Myers Feb. 8, 1944 2,345,129 Kuhn Mar. 28, 1944 2,653,903 Kilpatrick Sept. 29, 1953 2,738,307 Beckberger Mar. 13, 1956 2,853,434 Moser Sept. 23, 1958 2,901,413 Newchurch et a1. Aug. 25, 1959 

1. IN A PROCESS FOR THERMALLY CRACKING A CRUDE PETROLEUM OIL ON A GRANULAR SOLID SUBSTANCE SELECTED FROM THE GROUP CONSISTING OF INERT HEAT-RESISTING NON-OXIDIZAOLE SOLIDS AND CARBONACEOUS SOLIDS AT TEMPERATURES OF 630*C. TO 900*C. FOR THE PRODUCTION OF GASEOUS OLEFINES THE IMPOROVEMENT WHICH COMPRISES SEPARATING THE INITIAL CRUDE PETROLEUM OIL INTO ESSENTIALLY TWO COMPONENTS A DISTILLATIOM RESIDUE AND A DISTILLATE FRACTION SAID DISTILLATE FRACTION AMOUNTING TO ABOUT 20 TO 70% BY WEIGHT WITH REFRENCE TO THE INITIAL OIL AND SAID RESIDUE CONSTITUTING SUBSTANTIALLY THE REMAINING PORTION BY WEIGHT WITH REFRENCE TO SAID INITIAL OIL THERMALLY CRACKING THE DISTILLATION RESIDUE IN A FIRST STAGE AT A TEMPERATURE OF ABOUT 680*C. TO 760*C. IN A FLUIDIZED LAYER OF SAID GRANULAR SOLID SUBSTANCE HAVING AT LEAST AN OUTER SHELL FORMED FROM COKE PRODUCED BY SAID CRACKING IN SAID FIRST STAGE, AND THERMALLY CRACKING THE DISTILLATE FRACTION IN A SECOND STAGE, ALSO ON A GRANULAR SOLID SUBSTANCE, AT A TEMPRATURE OF ABOUT 750*C. TO 870*C. BUT AT LEAST ABOUT 40*C. HIGHER THAN THE TEMPERATURE IN SAID FIRST STAGE. 